Reaction Steps
To a stirred solution of 3-(6-[2,2′]bithiophenyl-5-yl-hexyloxymethyl)-3-ethyl-oxetane (6.0 g, 16.46 mmol) in anhydrous THF (100 ml) is added n-butyllithium (2.5 M in hexanes, 7.0 ml, 17.50 mmol) dropwise at −78° C. under nitrogen. After complete addition, the mixture is allowed to warm to room temperature, with stirring, over 2 h, followed by the addition of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (3.26 g, 17.5 mmol). The resultant mixture is stirred overnight at room temperature. The reaction is quenched with sat. aq. NH4Cl, and the reaction mixture is extracted with ethyl acetate (3×100 ml). The combined organic extracts are washed with water, brine, and dried over sodium sulphate. The solvent is removed under reduced pressure and the residue is further purified by column chromatography on silica, eluting with petroleum ether/ethyl acetate (9:1 to 4:1), to give 2-{5′-[6-(3-ethyl-oxetan-3-ylmethoxy)hexyl]-[2,2′]bithiophenyl-5-yl}-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane as a blue oil (4.53 g, 56%). 1H NMR (300 MHz, CDCl3): δ (ppm) 7.49 (d, J=3.6 Hz, 1H, Ar—H), 7.14 (d, J=3.6 Hz, 1H, Ar—H), 7.03 (d, J=3.6 Hz, 1H, Ar—H), 6.66 (d, J=3.6 Hz, 1H, Ar—H), 4.43 (d, J=5.8 Hz, 2H, OCH2), 4.34 (d, J=5.8 Hz, 2H, OCH2), 3.48 (s, 2H, OCH2), 3.42 (t, J=6.6 Hz, 2H, OCH2), 2.76 (t, J=7.5 Hz, 2H, ArCH2), 1.32-1.75 (m, 22H, CH2 and CH3), 0.86 (t, J=7.5 Hz, 3H, CH3); 13C NMR (75 MHz, CDCl3): δ (ppm) 144.8 (quat.), 143.7 (quat.), 137.0 (CH), 133.7 (quat.), 124.0 (CH), 123.1 (CH), 123.0 (CH), 83.1 (quat.), 77.5 (OCH2), 72.4 (OCH2), 70.4 (OCH2), 42.4 (quat.), 30.5 (CH2), 29.1 (CH2), 28.4 (CH2), 27.8 (CH2) 25.8 (CH2), 24.9 (CH3), 8.3 (CH3); MS (m/e): 490 (M+, 16%) □305 (79), 223 (25), 205 (100).
